https://www.sslsupportdesk.com/how-to-move-ssl-certificate-from-iis-7-to-iis-8/
https://support.rackspace.com/how-to/install-ssl-certificates-on-windows-server-2008r2-and-2012/
https://docs.microsoft.com/en-us/iis/get-started/whats-new-in-iis-8/iis-80-server-name-indication-sni-ssl-scalability (multiple ssl certificates on iis 8.0)
https://community.letsencrypt.org/t/dns-provider-not-allowing-txt-records-to-be-submitted-correctly-letsencrypt-validation-doesnt-pass/31201 (letsencrypt validation by dns challenge , dns-01)
Windows 2012/IIS8多网站用相同端口部署多张证书（SNI）: https://www.jb51.net/article/137427.htm